Substrates such as glass and steel are used to make buildings, appliances, cars, etc. Oftentimes, it is necessary to apply a functional coating(s) over the substrate to achieve certain performance properties. Examples of functional coatings are electroconductive coatings, photocatalytic coatings, low emissivity coatings, hydrophilic coatings, hydrophobic coatings, anti-reflective coatings, etc.
The functional coating is typically deposited directly on the substrate. Sometimes, when the functional coating is deposited directly on the substrate, the coated substrate does not achieve all of the desired performance properties (i.e., the required durability, the required aesthetic properties, etc.). For example, a coated substrate having a functional coating applied directly on the substrate may fail to exhibit a desired level of photocatalytic activity (PCA). Sometimes, a coated substrate is desirable that exhibits a higher PCA in certain environments such as environments where there is heavy soiling and/or low exposure to UV light.
The present invention provides coated substrates that include specific undercoating layers which have been found to enable the coated substrates to exhibit higher levels of photocatalytic activity than the same coated substrate would exhibit without the undercoating layer. The coated substrates, which include an undercoating layer exhibit, 1.5 to 2 times the photocatalytic activity of the same coated substrate without the undercoating. The undercoating layer can also be manipulated to provide a coated substrate with the desired aesthetic properties, for example, a neutral colored appearance.